ABSTRACT/SUMMARY Significance of the problem: Immunotherapeutic approaches are unsuccessful for most tumors with low mutational loads (i.e., few neoantigens eliciting robust T-cell activation) and few tumor-infiltrating lymphocytes (?cold? tumors). Our preclinical studies involving multiple mouse models indicate that combining a Sindbis virus (SV)?based immunotherapeutic approach with immunomodulatory antibodies (Abs) (e.g., to OX40), leads to regression-free survival by driving activated T cells into cold tumors. The treatment changes the transcriptome signature and metabolic program of T cells, driving the development of highly activated, terminally differentiated, effector T cells with enhanced tumor infiltration capacity despite a repressive tumor microenvironment (TME). Description of the product: We propose to develop innovative third-generation SV vectors to drive activated T cells into ?cold? tumors or tumors such as epithelial ovarian cancer (EOC), where a number of factors in the TME impair the presence or activity of TILs. One of these, CYN103, will encode a single-chain antibody (scFV) to OX40 and the full-length tumor-associated antigen (TAA) NY-ESO-1,expressed in about 40% of EOC cells. Therapeutic development: Early in 2020 Cynvec will begin a Phase 1 clinical trial of a SV vector, CYN102, which encodes NY-ESO-1 in women with chemotherapy-resistant EOC to establish its clinical safety. Given that CYN102 in combination with immunomodulatory Abs has curative effects in preclinical models, we will follow this trial with a Phase 1b trial to evaluate the safety and optimal dosing of CYN103 in women with EOC. Technical innovation of the product: ?Armed? SV vectors like CYN103, which encode their own agonistic/antagonistic scFVs or small ligands, can potentially overcome the inherent limitations that curtail efficacy of Abs, such as poor tissue or tumor penetrance and the potential of detrimental Fc-effector functions to deplete immune cells. Also, approved Abs are expensive, and their side effects limit their clinical use. Phase I (Year 1): 1. Engineer third-generation SV vectors for cancer immunotherapy, one of which, CYN103, will carry a dual payload designed to target EOC for use in planned Phase 1b trial. 2. Test and compare the efficacy of (i) CYN103, (ii) a vector encoding NY-ESO-1 only (CYN102), and (iii) a vector encoding scFV to OX40 only in a preclinical syngeneic model of EOC. Milestones: Generation of the CYN103 vector. Show equivalent anti-tumor efficacy in an EOC preclinical model to the combination of CYN102 and anti-OX40. Phase II (Years 2 & 3): 1. Produce CYN103 under Good Manufacturing Practice conditions. 2. Submit an Investigational New Drug (IND) application for CYN103. Milestones: GMP production of clinical grade CYN103. Obtain the preclinical and regulatory data needed to support an IND for a Phase 1b trial of CYN103. Commercial opportunity: EOC treatment in the US costs ~$5?6 billion annually. The size of the market and the high likelihood of resistance to existing therapies create a significant opportunity for novel therapies like ours.